Vehicles increasingly contain rechargeable devices, typically having NiCad batteries. In particular, utility trucks, police vehicles, and public safety vehicles carry a large number of devices including rechargeable flashlights, cell phones, portable radios, and computers. These devices may include battery voltages of less then 12 Volts, but have charging circuits adapted to accept 12 Volts for charging from vehicle 12 Volt batteries.
The rechargeable device charging circuits are often designed for small size or low cost, and may be inefficient, drawing more power than necessary to charge the devices. Even when efficient, the charging devices often continually charge the device batteries, after the devices are fully charged. The unneeded energy is dissipated as heat. Other devices, such as two-way radios, mobile dispatch terminals and siren controls do not typically use rechargeable batteries, but can continue to draw power if left on.
In commercial vehicles, the rechargeable devices are present in moderate numbers, and left in vehicles overnight, even over weekends. The draw on the vehicle batteries accumulates over time, and can leave vehicles with dead batteries. The problem is exacerbated in cold weather, as battery capacity decreases with decreasing temperature. Public safety vehicles left near the driver's residence rather than near central garages are particularly inconvenienced, as having the vehicle jump started or quickly charged may be problematic. In a typical scenario, a police vehicle in a remote area cannot respond because of a dead battery due to several devices having been charged for long periods, similar to leaving a dome light on.
The typical daily cycle for public safety vehicles such as patrol vehicles does not lend itself to the cycle of rechargeable batteries. Most patrol vehicles and the accessories inside the car are in use during the officers shift, and then need to be recharged when the vehicle is off. If the accessories are wired up to constantly recharge, then during engine off periods the vehicles battery is being discharged and will eventually lead to vehicle battery depletion. If the accessories are wired up to only recharge while the vehicles motor is running, the batteries in the accessories may not be fully charged, depending on vehicle "on" time.
What is desirable and has not been provided is a device for supplying power to rechargeable devices for a limited time after the ignition switch is turned off. What has not been provided is a device for supplying power to multiple rechargeable devices for differing time periods simultaneously. A configurable device delivering power for user selectable time intervals also has not been provided.